Fig. 31.1
Upper panel reveals a young woman who presented with acute generalized photo-induced erythema, acral vasculopathy of the fingers and toes, oral erosions, and proteinuria, all features of systemic lupus erythematosus. Lower panel reveals an elderly woman with dermatomyositis. Note the brightly red erythema sparing sun-protected sites
Case
A patient presents with a few to several weeks’ history of confluent red smooth macules and patches. The onset may be acute or insidious and favors photo-exposed sites. This presentation is exclusive of the patients with total skin erythroderma, in whom the differential diagnosis is different (see Chap. 26 on exfoliative erythroderma).
Clinical Differential Diagnosis
Depends on the onset and duration of the eruption. If acute and short-lived, then the patient is likely to have morbilliform drug eruption or exanthem (not addressed here); and if subacute to chronic, then
dermatomyositis, DM
photosensitive rash of systemic lupus erythematosus, SLE
photosensitive dermatitis/photo-drug eruption, and
subacute cutaneous lupus erythematosus, SCLE.
Clinical Clues
Lesions of SCLE are almost always discrete (annular polycyclic or psoriasiform, and rarely pityriasiform), unlike those of DM and the photosensitive rash of SLE , which are often diffuse. However, SCLE has been described as presenting in a diffuse manner as exfoliative erythroderma, even with bullae and TEN-like presentation. In my experience, this occurs in patients who are extremely photosensitive, following excessive sun exposure, resulting in the first episode of SCLE in an unsuspecting patient. Few patients with SCLE may have mild SLE.
The first episode of the photosensitive eruption in patients with undiagnosed SLE or DM may appear similar to and be confused with photosensitive drug eruption . Involvement of the eyelids with edema and purplish erythema is a characteristic of DM, while erythema, in the butterfly distribution, in the absence of eyelid involvement strongly favors SLE.
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